Camshaft & Dual (3X & 18X) Crankshaft Sensors

The Camshaft Position (CMP) sensor is located on the timing cover behind water pump, near camshaft sprocket. The dual (3X and 18X) Crankshaft Position (CKP) sensor is located behind the crankshaft balancer.

The PCM uses camshaft "sync-pulse" signals (passed to PCM by the ignition control module) to determine the exact position of piston No. 1. Signal is used by PCM to properly initialize fuel injector firing. If CMP sensor fails, engine can be restarted and will run in sequential mode; however, odds are one in 6 that injectors will spray correctly without CMP sensor signal. This provides "walk home" protection against CMP sensor failure.

In addition to the camshaft sensor, the crankshaft sensor contains 2 Hall Effect switches mounted in-between the interrupter rings. The outer interrupter ring located on the back side of the balancer, contains 18 evenly spaced blades, producing 18 pulses per crankshaft revolution. The inner ring has 3 unequal-width blades spaced at irregular intervals (10, 20 and 30 degrees apart).

The ignition control module monitors signals generated by the 2 Hall Effect switches. The 18X switch will change state once during the 10-degree gap of the 3X ring, twice during the 20-degree gap and 3 times during the 30-degree gap. The changing relationship between the 2 switch signals allows the ignition control module to identify the correct ignition coil to fire within the first 120 degrees of crankshaft rotation. This system provides for a faster start and a more accurate measurement of CKP sensor signals.

If the 3X signal to ignition control module is lost while the engine is running, the fuel injection system will continue to run in sequential mode; however, loss of 3X or 18X signal will prevent vehicle from restarting. If CMP sensor or dual CKP sensor signal is lost, a diagnostic trouble code will be set.